Preheat oven to 180 C / Gas 4. Grease two 15cm cake tins then line with baking parchment.
Combine the butter and sugar in a mixing bowl and beat until creamy using a handheld electric whisk. Add the eggs, one at a time, beating well after each addition. Gradually sift in the flour, and continue mixing until smooth. Add the vanilla extract and whisk for a further 2 minutes. Divide the mixture between the prepared cake tins.
Bake in the preheated oven for 40 minutes or until skewer inserted into the centre comes out clean.
For the cream:
Meanwhile, whisk the double cream milk with mascarpone cheese, sugar and vanilla extract until smooth, creamy and thick. Cover and chill in the fridge until the cake is ready to be decorated.
Remove the cake from the oven and let cool for 5 minutes in the tin. Turn out onto a cooling rack and cool completely. Once cool, carefully cut each cake in half horizontally to form 4 layers.
To assemble, place one layer on a serving plate as the base and cover with a third of the cream and berries. Repeat with the other 3 layers. Garnish with fresh mint leaves and dust with icing sugar.